Measuring broadcast audiences is a matter of longstanding concern to broadcasters and advertisers because audience measurements provide the data from which the effectiveness of broadcast programs and advertisements may be evaluated. A variety of well known methods have been employed in order to provide an estimate of the total audience to a program, to a portion of a program, and/or to a commercial. These methods also provide additional detailed estimates of demographically significant audience segments (e.g. the number of women aged 18-34 who watched a given minute of a selected program). Many of these methods involve manually and/or automatically measuring the viewing habits of the members, usually referred to as panelists or viewers, of statistically selected households.
The measurement of the viewing habits of a viewing audience generally requires three separate measurements: 1) a measurement of the channels or stations to which the viewing equipment (i.e. receiver) within a statistically selected household is tuned; 2) a measurement of the programs which were available at the times during which the viewing equipment was tuned to the viewed channels; and, 3) a measurement of the household members who were actually in front of the viewing equipment at the times that the viewing equipment was tuned to the measured channels.
The first of these measurements has long been made in sampled households with equipment that requires no active participation on the part of the viewer. For example, the system disclosed by Haselwood et al in U.S. Pat. No. 3,651,471 collects a real-time log of time-stamped tuning events for subsequent retrieval via a public switched telephone network. Later equipment, such as taught by Waechter et al in U.S. Pat. No. 4,943,963 provides, inter alia, the capability of editing the logged data prior to the transmission of the logged data to a data collection center.
The second of the above enumerated measurements has been done in a variety of ways, none of which involve either the active or the passive participation of the members of sampled households. For example, the system disclosed by Haselwood et al in U.S. Pat. No. 4,025,851 encodes a program or a commercial with an identification code which can be monitored in the field to verify (a) that a program or commercial has been broadcast and (b) the time of the broadcast. As another example, the system disclosed in U.S. Pat. No. 4,677,466 employs pattern recognition to verify both the fact and the time that a program or commercial has been broadcast.
The third of the above enumerated measurements has generally required some level of active participation by viewers. Widely used methods for measuring the composition of a television viewing audience have included the use of viewing diaries (in which a viewer manually logs a record of his or her viewing activity in a booklet that is physically returned to a data collection center) or by electronic "pushbutton" terminals (in which each viewer manually indicates his or her presence by the use of a small keyboard). A major shortcoming of these audience measurement systems is that such systems require some degree of active participation on the part of the viewer. This requirement is believed to reduce viewer cooperation and, as a result, to impair the statistical quality of the measurement.
Currey et al in U.S. Pat. No. 3,056,135 disclose an early, mostly passive, method of measuring a viewing audience. This method provides a record of the number and identity of persons in an audience by utilizing strategically placed switches for counting the number of persons entering, leaving, and remaining within a particular area, and a photographic recorder for periodically recording the composition of the audience. This approach requires that the photographic record be viewed by an operator, which both invades the viewers' privacy and imposes an unacceptable cost on the measurement operation.
The absence of an acceptable approach to identifying individual viewers passively led to a variety of suggestions for passive, non-obtrusive methods of counting (but not identifying) viewers and of tracking their movements about the viewing area. Notable among these is the teaching by Kiewit and Lu in U.S. Pat. No. 4,644,509 of an ultrasonic sonar system. The various passive methods of audience counting and tracking that have been suggested have found little acceptance in commercial practice for the fundamental reason that such methods fail to identify the members of the viewing audience. Furthermore, if the individual members of a sampled household are not uniquely identified, the various demographic information usually provided in viewing reports is not, generally speaking, readily ascertainable.
Methods aimed at providing unique viewer identity while reducing, but not eliminating, an active effort on the part of the viewer are also known. These methods have included the use of electronically active tags that can be used to indicate a viewer's presence. Devices of this sort have been taught, inter alia, by Kiewit in U.S. Pat. No. 4,930,011. Such systems are not truly "passive" because the viewer is required to make a conscious, ongoing effort to wear, or be in possession of, the tag.
More recently, passive, non-obtrusive methods of audience measurement have been taught by Lu in U.S. Pat. Nos. 4,858,000 and 5,031,228. The disclosures of these U.S. Pat. Nos. 4,858,000 and 5,031,228 are herein incorporated by reference. These patents teach an automatic system that uses a video camera to acquire an image of the face of a television audience member, and a computer subsystem to recognize that facial image by comparing that facial image to reference facial images stored in a data base. This system also includes passive infrared scanners for locating and tracking viewers, and covert near-infrared illuminators that provide a controllable level of illumination for the video camera. Camera systems of the sort taught in these patents have been shown to be capable of correctly identifying a known member of a television audience most of the time when the known member is seated with his or her face turned toward the television set and is in a reasonably well-lighted area. Such systems, however, fail to identify a viewer whose head is turned away from the camera, or who is entering or leaving the viewing area. In other words, a known person, who is present in the viewing area, can only be identified by prior art passive audience measurement systems for a fraction of a monitored time period. Furthermore, the system taught by Lu in U.S. Pat. Nos. 4,858,000 and 5,031,228 uses a single video camera and a mechanical scanning mechanism to cover a wide field of view. The noise of this mechanical scanning mechanism can disturb viewers in the viewing area.
Similarly, individuals can be identified and tracked for marketing research applications in environments other than television audience situations. Luet al, in U.S. Pat. No. 5,331,544, which was issued on Jul. 19, 1994, teach a system and method for identifying shoppers within a retail store and for correlating the identity of these shoppers with their purchases and with their responses to advertisements. The disclosure of U.S. Pat. No. 5,331,544 is herein incorporated by reference.